ILOILO – The poor construction of the P680-million flyover in Barangay Ungka II, Pavia, Iloilo is costing taxpayers at least P250 million more.
Third-party consulting firm Abinales Associates Engineers + Consultants has recommended that Department of Public Works and Highways (DPWH) repair the vertical displacement at piers 4, 5 and 6 of the flyover.
It presented the results of its geotechnical investigation of the Ungka flyover during yesterday’s meeting of the Regional Development Council’s (RDC) Infrastructure Development Committee (IDC) chaired by Iloilo City’s Mayor Jerry Treñas at the RDC Hall of the National Economic and Development Authority (NEDA) Region 6.
“Medyo malaking pondo ang kailangan dito. Nasa P250 million ang minimum kasi depende ‘yan sa kalalabasan ng grouting din. Pero we are looking as deep as 100 meters para sigurado na hindi na mag-settle,” said Adam Abinales, managing partner of Abinales Associates Engineers + Consultants.
The Ungka flyover was opened to traffic on the second week of September 2022. But after just two weeks, DPWH closed it due to vertical displacement. Three piers were found to be sinking.
Abinales gave a 10-month timeline to complete the recommended rectifications.
Undersecretary Roberto R. Bernardo said DPWH would try to have the P250 million included in the 2024 budget.
“We are looking at the 2024 budget kasi we cannot source out ‘yong 2023. So, ‘yong option is 2024 at the earliest,” said Bernardo.
Once funds are available by January 2024, DPWH will start bidding for qualified contractors, after which the 10-month timeline to complete the rectifications will begin.
Completion of rectification work is expected around the last quarter of December 2024 or the first quarter of 2025.
“Assuming na may available na pondo, kung magkaroon by January 2024, 10 months ‘yong count at the most matatapos ‘yong rectifications,” said Bernardo.
Abinales said they bore holes on all 16 piers of the flyover.
A borehole, according to Trenchlesspedia.com, is a hole that is bored beneath the ground during a geotechnical evaluation of a design pathway for the installation of underground services. Conceptually similar to potholing, a borehole provides information about the design pathway itself.
The boreholes showed that the nature of the soil beneath piers 4, 5 and 6 is soft despite digging 55 meters for the piers’ bases.
“Lumalabas sa resulta ng aming investigation na medyo malambot talaga ang lupa. Hindi pa naabot ‘yong hard strata, up to 55 meters, hindi pa rin sia matigas,” said Abinales.
Below is the cumulative settlement recorded on piers 4, 5 and 6 from May 13, 2022 to April 14, 2023.
- pier 4 – 431 millimeters
- pier 5 – 583 millimeters
- pier 6 – 488 millimeters
Abinales also confirmed that there is minimal vertical displacement on the other remaining piers.
Below is the cumulative settlement recorded in the same period:
- pier 1 – 82 millimeters
- pier 2 – 151 millimeters
- pier 3 – 150 millimeters
- pier 7 – 20 millimeters
- pier 8 – 17 millimeters
- pier 9 – 21 millimeters
- pier 10 – 20 millimeters
- pier 11 – 70 millimeters
- pier 12 – 88 millimeters
- pier 13 – 114 millimeters
- pier 14 – 41 millimeters
- pier 15 – 51 millimeters
- pier 16 -27 millimeters
“The other piers, medyo hindi sia malaki,” added Abinales.
Recommended schemes of rectification
Three recommended schemes of rectification were presented by Abinales during the meeting:
* Scheme 1: Provide additional bored piles.
Pros – Group pile capacity will be significantly increased to sustain the required demand capacity at the pier base.
Cons – In order to drive the additional bored piles, affected existing prestressed concrete (PSC) girders on coping beams will be removed and replaced, if necessary since large equipment shall be used for drilling and driving bored piles.
* Scheme 2: Provide a portal frame to support the existing PSC girders.
Cons – In order to drive the new bored piles to construct and support the portal frame, right-of-way acquisition will be a great challenge; the portal frame will ignore the effect of the existing piers to support the PSC girders already installed.
* Scheme 3: Underpinning the existing piers and abutments, including existing bored piles, by intense jet grouting.
Pros – Underpinning will only require at least three meters of vertical clearance; therefore, existing PSC girders may not need to be removed and replaced.
Cons – Quantities of staged grouting will depend on the actual soil condition and stratum to develop the required pile capacity to sustain the demand load capacity at each pier/abutment. This scheme should be handled by the specialty contractor in intensive jet grouting, which is a proprietary specialty work. Verification is required by performing a static load test of the jet grouting.
Abinales recommended Scheme 1, or providing additional bored piles, as more feasible.
“‘Yong piers 4 ,5 and 6 kailangan natin ang additional bored piles na malalim talaga para ma-sustain ‘yong load capacity,” he said.
The firm’s representative also recommended to the DPWH that it should remove and replace the girders on piers 4, 5 and 6 to give way during the construction of additional bored piles.
Abinales said the additional bored piles at piers 4, 5 and 6 should have a depth of 40 meters or more. Currently, the bored piles are only 28 meters deep in pier 4 and 26 meters deep in piers 5 and 6.
“‘Yong piers, ‘yon pa rin yon, lalakihan lang sia ng kaunti, magkaroon lang ng jacketing,” he explained when asked if the current posts in piers 4, 5 and 6 would be removed.
He added there is no need to reach the hard strata or bedrock to bury the bored piles, but it helps to prevent settlement if there are several board piles buried deep enough.
“Dinadamihan namin ang bored piles para kahit hindi malalim kaya pa rin. Maraming engineering solutions, hindi lang isa eh. Damihan ‘yong pilote o ‘di kaya isa lang pilote pero dapat malalim,” he said.
Despite having naturally soft soil, Abinales clarified that as long as there is sufficient geotechnical study, heavy structures could still be built in Barangay Ungka II.
For the remaining piers, the consulting firm suggested the conduct of jet grouting under Scheme 3, or underpinning the existing piers and abutments, including existing bored piles, by intense jet grouting.
The jet grouting should be 100 meters deep to prevent settlement, added Abinales.
Also present during the meeting were NEDA-6 director Arecio Casing Jr., Iloilo’s Gov. Arthur Defensor Jr., Iloilo City’s Vice Mayor Jeffrey Ganzon, DPWH-6 director Nerie Bueno, DPWH-6 assistant director Jose Al Fruto, Iloilo City councilors Ely Estante and Sedfrey Cabaluna, Philippine Chamber of Commerce & Industry Region 6 governor Atty. Jobert Peñaflorida, RDC-6’s IDC co-chair Marisa Segovia, and Pavia’s Mayor Luigi Gorriceta, among others./PN
